The present invention relates to a composition comprising at least one fluorochemical polyether silane compound having a polyfluoropolyether segment and at least two hydrolysable silane groups per molecule with one or more non-fluorinated compounds having at least two hydrolysable groups per molecule. The present invention also relates to a composition comprising a partial condensate resulting from a partial condensation reaction between the fluorochemical polyether silane compound having a polyfluoropolyether segment and at least two hydrolysable silane groups per molecule with one or more non-fluorinated compounds having at least two hydrolysable groups per molecule. The present invention also relates to the use of the compositions for providing durable repellency to water, oil and stain to a substrate.
In the past, various efforts have been made to provide repellent properties to a substrate. For example, U.S. Pat. No. 4,687,707 (=EP-A-0 166 363) describes a low reflectance, transparent material having anti-soiling properties, which comprises a transparent substrate having a coating comprising a thin layer of a condensation product of a fluorine containing silicon compound having a polyfluorinated or perfluorinated carbon chain.
WO 99/03941 relates to a coating material comprising condensates of at least one compound (A) of the general formula RaMZb (a=0 to 3; b=1 to 4; a+b=3, 4), and at least one compound (B) of the general formula Rxe2x80x2xMZy (x=1 to 3; y=1 to 3; x+y=3,4), wherein R is a non-hydrolysable organic group, M is an element selected from the main groups III to V or from the subgroups II to IV of the periodic table of elements, Z is a hydrolysable group, and at least one Rxe2x80x2 contains a perfluoropolyether structure separated from M by at least two atoms, and at least one R is not equal to at least one Rxe2x80x2. The composition is used to provide oleophobic properties to substrates, such as porous polymers.
U.S. Pat. No. 5,739,369 (=EP-A-0 738 771) relates to a water-soluble surface treating agent comprising the reaction product of (A) a fluoroalkyl group-containing alkoxysilane with (B) an amino-group-containing alkoxysilane and optionally further with (C) an alkyl group-containing alkoxysilane. The agent is diluted with water to form a solution for treating glass and other substrates to impart thereto properties, such as water repellency.
U.S. Pat. No. 5,919,886 relates to a fluorine-containing organo-silicon compound useful for obtaining elastomers and to room temperature curable silicon compositions containing the same compound.
U.S. Pat. No. 5,306,758 (=EP-A-0 433 070) describes fluorocarbon based, curable, crosslinkable compositions and coatings prepared therefrom that can be used to form low-surface energy release liners.
U.S. Pat. No. 5,922,787 (=EP-0 797 111) relates to a composition containing an alkoxy-silane compound having a perfluoropolyether group. The composition may be used for forming an anti-fouling film.
However, our findings indicate that while some of the previously known surface coatings may be capable of providing acceptable levels of initial repellent properties, a loss of repellency is often encountered due to abrasion of the coating.
Accordingly, it is desirable to provide a coating composition capable of providing a highly durable water, oil and/or stain repellent coating on a substrate. In particular, it is desirable to provide a durable coating wherein the initial, repellent properties are substantially maintained, even under abrading conditions. Further, the coating compositions preferably can be applied and used in an environmental friendly way and can be produced in a reliable, convenient and cost effective way. Additionally, the coatings desirably have a good durability against exposure to UV light, i.e. the repellency properties do not substantially degrade upon exposure to UV light. Furthermore, it is desirable to obtain optically clear coatings in particular when transparent substrates such as glass are to be treated with the compositions. It would also be desirable to obtain the desired repellency properties without the need for subjecting the coated substrate to a heat treatment at elevated temperature.
In one aspect, the present invention provides a composition comprising (A) one or more fluorochemical polyether silane compound(s) having a polyfluoropolyether segment and at least two silane groups xe2x80x94Si(Y)3-x(R1)x per molecule, wherein R1 represents an alkyl group, Y represents a hydrolysable group and x is 0 or 1; and (B) a substantial amount of one or more non-fluorinated compounds of an element M selected from the group consisting of Si, Ti, Zr, B, Al, Ge, V, Pb, Sn and Zn and having at least two hydrolysable groups per molecule. In another aspect the present invention provides the reaction product of (A) and (B).
In a further aspect, the present invention provides a composition derivable from a partial condensation of the above defined composition. By xe2x80x9cpartial condensationxe2x80x9d and xe2x80x9cpartial condensatexe2x80x9d in connection with the present invention is meant that some of the hydrolysable groups in the mixture have reacted while leaving a substantial amount of hydrolysable groups available for a condensation reaction. Typically, a partial condensate means that at least 20%, preferably at least 30%, more preferably at least 50% of the hydrolysable groups are still available for condensation reaction.
In a still further aspect, the present invention also provides a method for treating a substrate, comprising the step of applying to at least a portion of the surface of the substrate the compositions as defined above. The fluorochemical compositions of the present invention can be used to treat substrates and are capable of rendering such substrates oil and water repellent and/or to provide stain repellency thereto.
The compositions are generally effective at low levels of application and have good durability. The compositions are particularly useful for rendering substrates such as ceramics, glass, inox and chromated steel, repellent to water and/or oil.
In a further aspect, the present invention also provides for compositions from which a composition as defined above can be readily prepared. Such compositions comprise components (A) and (B) and are substantially free of water. By substantially free of water is meant that the compositions do not contain water or the amount of water is so low that reaction between components (A) and (B) does not occur in such composition. Preferably, these compositions are also free of acid or base catalyst and will conveniently contain an amount of organic solvent so as to obtain a homogeneous mixture.
By the term xe2x80x9chomogeneous mixturexe2x80x9d in connection with the present invention is meant that the composition is stable, for at least 24 hours, preferably 1 month, at room temperature. Some haziness may occur, however without substantial precipitation or phase separation occurring.
The term xe2x80x9chydrolysable groupxe2x80x9d in connection with the present invention refers to a group which either is directly capable of undergoing condensation reactions under appropriate conditions or which is capable of hydrolyzing under appropriate conditions, thereby yielding a compound, which is capable of undergoing condensation reactions. Appropriate conditions include acidic or basic aqueous conditions, optionally in the presence of a condensation catalyst.
Accordingly, the term xe2x80x9cnon-hydrolysable groupxe2x80x9d as used in the present invention refers to a group not capable of either directly undergoing condensation reactions under appropriate conditions or of hydrolyzing under the conditions listed above for hydrolyzing the hydrolyzable groups.
The term xe2x80x9csubstantial amountxe2x80x9d of a compound as used herein refers to an amount of a compound greater than a catalytic amount of that compound necessary for promoting a certain reaction (e.g., condensation reactions). Accordingly, a composition comprising a substantial amount of that compound generally allows the compound to act as a reactant such that the resulting product is formed of at least part of that compound.
Component (A) comprises at least one fluorochemical polyether silane compound having a polyfluoropolyether segment and at least two silane groups xe2x80x94Si(Y)3-x(R1)x per molecule, wherein R1 represents an alkyl group (for example a C1-C8, preferably C1-C4 primary or secondary alkyl group), Y represents a hydrolysable group and x is 0 or 1.
Preferably, component (A) is a fluorochemical polyether silane compound according to formula (I)
Rf[Qxe2x80x94C(R)2xe2x80x94Si(Y)3-x(R1)x]zxe2x80x83xe2x80x83(I) 
wherein Rf represents a multivalent polyfluoropolyether segment, Q represents an organic divalent linking group, R1 represents an alkyl group (preferably containing 1 to 8, more preferably 1 to 4 carbon atoms), Y represents a hydrolysable group; R represents hydrogen or an alkyl group of 1 to 4 carbon atoms and the R groups may be the same or different, x is 0 or 1 and z is 2, 3 or 4. Preferably both R groups are hydrogens.
The hydrolysable groups Y may be the same or different and are generally capable of hydrolyzing under appropriate conditions, for example under acidic or basic aqueous conditions, such that the fluorochemical silane compound can then undergo condensation reactions. Preferably, the hydrolysable groups upon hydrolysis yield groups capable of undergoing condensation reactions, such as silanol groups.
Examples of hydrolysable groups include halide groups, such as chlorine, bromine, iodine or fluorine, alkoxy groups xe2x80x94ORxe2x80x2 (wherein Rxe2x80x2 represents a lower alkyl group, preferably containing 1 to 6, more preferably 1 to 4 carbon atoms and which may optionally be substituted by one or more halogen atoms), acyloxy groups xe2x80x94O(CO)xe2x80x94Rxe2x80x3 (wherein Rxe2x80x3 represents a lower alkyl group, preferably containing 1 to 6, more preferably 1 to 4 carbon atoms, which may be optionally substituted by one or more halogen atoms), aryloxy groups xe2x80x94ORxe2x80x3xe2x80x2 (wherein Rxe2x80x3xe2x80x2 represents an aryl moiety, preferably containing 6 to 12, more preferably containing 6 to 10 carbon atoms, which may be optionally substituted by one or more substituents independently selected from halogens, and C1-C4 alkyl groups which may optionally be substituted by one or more halogen atoms). In the above formulae Rxe2x80x2, Rxe2x80x3, and Rxe2x80x3xe2x80x2 may include branched structures.
Suitable hydrolysable groups also include polyoxyalkylene groups of the formula
xe2x80x94Oxe2x80x94Axe2x80x94R3 
wherein A is a divalent hydrophilic group (a) having the formula
(CHR4xe2x80x94CH2Oxe2x80x94)q 
wherein q is a number having a value of 1 to 40, preferably 2 to 10, R4 is hydrogen or methyl, and at least 70% of R4 is hydrogen, and R3 independently is hydrogen or a lower alkyl group having 1 to 4 carbon atoms, such as disclosed in U.S. Pat. No. 5,274,159, incorporated herein by reference.
Specific examples of hydrolysable groups include methoxy, ethoxy and propoxy groups, chlorine and an acetoxy group. Particularly preferred hydrolysable groups include C1-C4 alkoxy groups, such as methoxy and ethoxy groups. C2-C4 alkoxy groups are preferred in case it is desired to obtain clear coatings on a substrate.
The divalent polyfluoropolyether group Rf in the above formula (I), representing the fluorinated polyether silane, can include linear, branched, and/or cyclic structures, that may be saturated or unsaturated, and containing one or more caternary oxygen atoms (i.e. one or more non-adjacent xe2x80x94CF2xe2x80x94 groups may be replaced by xe2x80x94Oxe2x80x94 groups). Rf preferably is a perfluorinated group (i.e., all Cxe2x80x94H bonds are replaced by Cxe2x80x94F bonds). More preferably, it includes perfluorinated repeating units selected from the group of xe2x80x94(CnF2nO)xe2x80x94, xe2x80x94(CF(Z)O)xe2x80x94, xe2x80x94(CF(Z)CnF2nO)xe2x80x94, xe2x80x94(CnF2nCF(Z)O)xe2x80x94, xe2x80x94(CF2CF(Z)O)xe2x80x94, and combinations thereof, wherein the repeating units generally may be randomly, blocky or alternating arranged, and optionally can include xe2x80x94(CnF2n)xe2x80x94 and xe2x80x94(CF(Z))xe2x80x94 units and wherein n in a number from 1 to 12 inclusive, preferably from 1 to 4 inclusive. Rf may also comprise cyclic perfluoro groups, for example cyclic xe2x80x94C6F10xe2x80x94 groups.
In these repeating units Z is a perfluoroalkyl group, an oxygen-containing perfluoroalkyl group, a perfluoroalkoxy group, or an oxygen-substituted perfluoroalkoxy group, all of which can be linear, branched, or cyclic, and preferably have about 1 to about 9 carbon atoms and 0 to about 4 oxygen atoms. Examples of polyfluoropolyethers containing polymeric moieties made of these repeating units are disclosed in U.S. Pat. No. 5,306,758 (Pellerite).
In one embodiment, approximate average structures for a divalent perfluoropolyether group include xe2x80x94CF2O(CF2O)m(C2F4O)pCF2xe2x80x94, wherein an average value for m is 0 to about 50 and an average value for p is 0 to about 50, with the proviso that both m and p are not simultaneously 0, xe2x80x94CF(CF3)xe2x80x94(OCF2CF(CF3))pOxe2x80x94Rfxe2x80x2xe2x80x94O(CF(CF3)CF2O)pCF(CF3)xe2x80x94, xe2x80x94CF2 O(C2F4O)pCF2xe2x80x94, and xe2x80x94(CF2)3O(C4F8O)p(CF2)3xe2x80x94, wherein Rfxe2x80x2 is a divalent, perfluoroalkylene group containing one or more carbons and optionally caternary O or N. The values of m and p in these approximate average structures can vary. Preferably, an average value of m is within a range of about 1 to about 50, and an average value of p is within a range of about 3 to about 40. As these are polymeric materials, such compounds exist as mixtures upon synthesis, which are suitable for use. The repeat units generally may be positioned in a random, blocked or alternating arrangement.
As synthesized, these structures typically include a mixture of polymeric units. The approximate average structure is the approximate average of the mixture of structures. Further, the distribution of perfluorinated repeating units may be regular or random.
The divalent linking group Q may be the same or different and can include linear, branched, or cyclic structures, that may be saturated or unsaturated, and preferably contains 1 to 15 atoms. The group Q can contain one or more heteroatoms (e.g., oxygen, nitrogen, or sulfur) and/or one or more functional groups (e.g., carbonyl, amide, urethane or sulfonamide). It can also be substituted with one or more halogen atoms (preferably, fluorine atoms), although this is less desirable, as this might lead to instability of the compound. The divalent linking group Q preferably is substantially stable against hydrolysis.
For example, Q may be a saturated or unsaturated hydrocarbon group typically including 1 to 15 carbons atoms. Preferably Q is a linear hydrocarbon group preferably containing 1 to 10 carbon atoms, and optionally containing 1 to 4 heteroatoms and/or 1 to 4 functional groups, and more preferably, containing at least one functional group.
Suitable linking groups Q include the following structures in addition to a covalent bond. For the purposes of this list, each k is independently an integer from 0 to about 20, kxe2x80x2 is independently an integer from 0 to 20, preferably from 2 to 12 and most preferably from 2 to 6, R1xe2x80x2 is hydrogen, phenyl, or alkyl of 1 to about 4 carbon atoms, and R2xe2x80x2 is alkyl of 1 to about 20 carbon atoms
Preferred linking groups Q are xe2x80x94C(O)NH(CH2)2xe2x80x94 and xe2x80x94OC(O)NH(CH2)2xe2x80x94.
Compounds of formula (I) that are conveniently used, generally have a molecular weight of at least about 650, and preferably, at least about 1000. It will be understood, with respect to the description of formula I, that the composition comprises mixtures of compounds and therefore mixtures of molecular weights.
Examples of preferred fluorinated disilanes (A) include, but are not limited to, the following approximate average structures:
(R1)x(Y)3-xSixe2x80x94CR2xe2x80x94QCF2O(CF2O)m(C2F4O)pCF2Qxe2x80x94CR2xe2x80x94Si(Y)3-x(R1)x, 
(R1)x(Y)3-xSixe2x80x94CR2xe2x80x94QCF(CF3)O[CF2CF(CF3)]m(CF2)pO[CF(CF3)CF2O]nCF(CH3)Qxe2x80x94CR2xe2x80x94Si(Y)3-x(R1)x 
(R1)x(Y)3-xSixe2x80x94CR2xe2x80x94QCF2O(C2F4O)pCF2Qxe2x80x94CR2xe2x80x94Si(Y)3-x(R1)x, and 
(R1)x(Y)3-xSixe2x80x94CR2xe2x80x94Q(CF2)3O(C4F8O)p(CF2)3Qxe2x80x94CR2xe2x80x94Si(Y)3-x(R1)x, 
Preferably, in each fluorinated polyether silane, Q contains a nitrogen atom. More preferably, at least one Qxe2x80x94CR2xe2x80x94Si(Y)3-x(R1)x, group per molecule is C(O)NH(CH2)3Si(OR)3 or OC(O)NH(CH2)3Si(OR)3 (wherein R is methyl, ethyl, polyethyleneoxy or mixtures thereof).
The compounds of formula (I) can be synthesized using standard techniques. For example, commercially available or readily synthesized perfluoropolyether esters (or function derivative thereof) can be combined with a functionalized alkoxysilane, such as a 3-aminopropylalkoxysilane, according to U.S. Pat. No. 3,810,874 (Mitsch et al.). It will be understood that functional groups other than esters may be used with equal facility to incorporate silane groups into a perfluoropolyether.
In accordance with a particular embodiment of the present invention, such perfluoropolyether esters may be prepared through direct fluorination of a hydrocarbon polyether diester. Direct fluorination involves contacting the hydrocarbon polyether diester with F2. Accordingly, the hydrogen atoms on the hydrocarbon polyether diester will be replaced with fluorine atoms thereby generally resulting in the corresponding perfluoropolyether diester. Direct fluorination methods are disclosed in, for example, U.S. Pat. Nos. 5,578,278 and 5,658,962, which are incorporated herein by reference.
Examples of intermediates suitable for use in the preparation of fluorochemical polyether silanes may be represented by the general formula Rfxe2x80x94Xz, wherein Rf is as previously defined for Formula I and z is 2, 3 or 4. A particularly useful intermediate may represented by the general formula
X(CF2)nxe2x80x94Oxe2x80x94Cnxe2x80x2F2nxe2x80x2xe2x80x94Oxe2x80x94(CF2)nX 
where n is in the range of 1 to 6, and preferably in the range of 1 to 3; nxe2x80x2 is in the range of 5 to 12, and preferably in the range of 5 to 7, X is selected from the group consisting of xe2x80x94COOH, xe2x80x94COOM1/v, xe2x80x94COONH4, xe2x80x94COOR, xe2x80x94CH2OH, xe2x80x94COF, xe2x80x94COCl, xe2x80x94COR, CONRxe2x80x2Rxe2x80x2, xe2x80x94CH2NH2, xe2x80x94CH2NCO, xe2x80x94CN, xe2x80x94CH2OSO2R, xe2x80x94CH2OCOR, xe2x80x94OC(O)CH3, xe2x80x94CH2OCOCRxe2x80x2xe2x95x90CH2, xe2x80x94CONH(CH2)mSi(OR)3, and xe2x80x94CH2O(CH2)mSi(OR)3;
where M is a metal atom having a valence xe2x80x9cvxe2x80x9d of 1 to 4, each R is independently selected from the group consisting of alkyl groups having from 1 to 14 carbon atoms, fluoroalkyl groups having from 1 to 14 carbon atoms, aryl groups having from 6 to 10 ring-carbon atoms, and heteroatom-containing groups having from 1 to 14 carbon atoms, and m is an integer in the range from 1 to 11; Rxe2x80x2 is independently H or R with the proviso Rxe2x80x2 is not a fluoroalkyl group.
Specific structures are exemplified by: 
It will be understood with respect to the above novel structures, that other functional groups may be substituted for those depicted. For examples, the xe2x80x94CO2H group may be substituted by xe2x80x94COOM1/v, xe2x80x94COONH4, xe2x80x94COOR, xe2x80x94CH2OH, xe2x80x94COF, xe2x80x94COCl, xe2x80x94COR, CONRxe2x80x2Rxe2x80x2, xe2x80x94CH2NH2, xe2x80x94CH2NCO, xe2x80x94CN, xe2x80x94CH2OSO2R, xe2x80x94CH2OCOR, xe2x80x94OC(O)CH3, xe2x80x94CH2OCOCRxe2x80x2xe2x95x90CH2, xe2x80x94CONH(CH2)mSi(OR)3, and xe2x80x94CH2O(CH2)mSi(OR)3 as previously described.
An additional embodiment is a composition comprising
X(CF2)nxe2x80x94Oxe2x80x94(CF2)qxe2x80x94(Cnxe2x80x2F2nxe2x80x2-2)xe2x80x94(CF2)qxe2x80x94Oxe2x80x94(CF2)nX 
where n is in the range of 1 to 6, and preferably in the range of 1 to 3; Cnxe2x80x2F2nxe2x80x2-2 represents a cycloalkylene moiety where nxe2x80x2 is in the range of 5 to 12, and preferably in the range of 6 to 8, X is selected from the group consisting of xe2x80x94COOH, xe2x80x94COOM1/v, xe2x80x94COONH4, xe2x80x94COOR, xe2x80x94CH2OH, xe2x80x94COF, xe2x80x94COCl, xe2x80x94CORxe2x80x2, CONRxe2x80x2Rxe2x80x2, xe2x80x94CH2NH2, xe2x80x94CH2NCO, xe2x80x94CN, xe2x80x94CH2OSO2R, xe2x80x94CH2OCOR, xe2x80x94OC(O)CH3, xe2x80x94CH2OCOCRxe2x80x2xe2x95x90CH2, xe2x80x94CONH(CH2)mSi(OR)3, xe2x80x94CH2O(CH2)mSi(OR)3; where M is a metal atom having a valence xe2x80x9cvxe2x80x9d of 1 to 4, each R is independently selected from the group consisting of alkyl groups having from 1 to 14 carbon atoms, fluoroalkyl groups having from 1 to 14 carbon atoms, aryl groups having from 6 to 10 ring-carbon atoms, and heteroatom-containing groups having from 1 to 14 carbon atoms, q is 0 or 1, and m is an integer in the range from 1 to 11; Rxe2x80x2 is independently H or R with the proviso Rxe2x80x2 is not a fluoroalkyl group.
Specific perfluorinated cycloalkylene-containing structures are exemplified by: 
In an alternative method, perfluoropolyetherdiols can be reacted with a functionalized alkoxysilane, such as 3-trimethoxysilylpropylisocyanate. Modifications of this method are described in the Examples. Such materials may or may not need to be purified before use in a treatment composition.
In the present invention, mixtures of compounds (A) and/or mixtures of compounds (B) may be used.
Component (B) as used in the present invention comprises one or more non-fluorinated compounds of an element M selected from the group consisting of Si, Ti, Zr, B, Al, Ge, V, Pb, Sn and Zn having at least two hydrolysable groups per molecule. Preferably, the hydrolysable groups are directly bonded to the element M.
In one embodiment of the present invention, component (B) comprises a compound according to the formula (II)
(R2)qM(Y1)p-qxe2x80x83xe2x80x83(II) 
wherein R2 represents a non-hydrolysable group, M represents an element of valency p+q, selected from the group consisting of Si, Ti, Zr, B, Al, Ge, V, Pb, Sn and Zn, p is 3 or 4 depending on the valence of M, q is 0, 1 or 2, and Y1 represents a hydrolysable group.
The hydrolysable groups present in component (B) may be the same or different and are generally capable of hydrolyzing under appropriate conditions, for example under acidic or basic aqueous conditions, such that component (B) can undergo condensation reactions. Preferably, the hydrolysable groups upon hydrolysis yield groups capable of undergoing condensation reactions, such as hydroxyl groups.
Typical and preferred examples of hydrolysable groups include those as described with respect to component (A). Preferably, component (B) includes tetra-, tri- or dialkoxy (preferably containing 1 to 4 carbon atoms) compounds.
The non-hydrolysable groups R2 may be the same or different and are generally not capable of hydrolyzing under the conditions listed above. For example, the non-hydrolysable groups R2 may be independently selected from a hydrocarbon group, for example a C1-C30 alkyl group, which may be straight chained or branched and may include one or more aliphatic, cyclic hydrocarbon structures, a C6-C30 aryl group (optionally substituted by one or more substituents selected from halogens and C1-C4 alkyl groups), or a C7-C30 aralkyl group.
In one embodiment the non-hydrolysable groups R2 are independently selected from a hydrocarbon group, for example a C1-C30 alkyl group and a C6-C20 aryl group (optionally substituted by one or more substituents selected from halogens and C1-C4 alkyl groups).
Preferred compounds (B) include those in which M is Ti, Zr, Si and Al. Representative examples of component (B) include tetramethoxysilane, tetra ethoxysilane, methyl triethoxysilane, dimethyldiethoxysilane, octadecyltriethoxysilane, methyl trichlorosilane, tetra-methyl orthotitanate, tetra ethyl orthotitanate, tetra-iso-propyl orthotitanate, tetra-n-propyl orthotitanate, tetraethyl zirconate, tetra-iso-propyl zirconate tetra-n-propyl zirconate and the like. More preferred compounds include C1-C4 alkoxy derivatives of Si, Ti and Zr. Particularly preferred compounds (B) include tetraethoxysilane. Single compounds or mixtures of compounds (B) may be used.
Optionally, the composition may comprise one or more crosslinking agents (C), in order to further increase the durability of the coating. Component (C) may be selected from compounds with additional functionality from those of components (A) and (B). For example, component (C) may comprise a compound of an element Ml that is selected from the group consisting of Si, Ti, Zr, B, Al, Ge, V, Pb, Sn and Zn having at least one hydrolysable group and at least one reactive functional group per molecule that is capable of engaging in a crosslinking reaction. Preferably, said at least one hydrolysable group is directly bonded to the element M1.
Suitable and preferred hydrolysable groups include those groups mentioned with respect to component (A). If component (C) includes more than one hydrolysable groups, these may be the same or different. Particularly preferred hydrolysable groups are selected from C1-C4 alkoxy groups, such as methoxy, ethoxy, iso- and (preferably) n-propoxy, or iso- and (preferably) n-butoxy groups.
The reactive functional group is a group which is capable of engaging in a crosslinking reaction so as to provide further crosslinking functionality to the polycondensation product that can be obtained from components (A), (B) and (C). The crosslinking reaction may involve for example irradiation, heating or a combination thereof. If component (C) includes more than one reactive functional groups, these groups may be the same or different. Of these, free radically polymerizable groups, such as vinyl, acrylate or methacrylate groups, are particularly preferred reactive functional groups.
A preferred crosslinking agent can be represented by formula (IV):
Lxe2x80x94Qxe2x80x94Si(Y)3-x(R1)x 
wherein
L represents a reactive functional group that may react by condensation or addition reactions such as an amino group, an epoxy group, a mercaptan or an anhydride group or by free-radical polymerization; and
Q, Y and R1 are as described for formula I, and x is 0, 1 or 2.
For formula V, preferably Q is an alkylene (preferably containing 1 to 10, more preferably containing 1 to 6 carbon atoms), an arylene (preferably containing 6 to 20 carbon atoms which may be substituted by one or more C1-C4 alkyl groups, halogen atoms or mixtures thereof), an oxyalkylene group of the formula (xe2x80x94Oxe2x80x94Rxe2x80x94)n, wherein R is independently selected from a divalent, straight chained or branched lower alkyl group (preferably containing 1 to 6 carbon atoms) and n is an integer from 1 to 20.
For formula IV, preferably R1 independently represents an alkyl group, preferably a C1-C8 alkyl group (such as methyl, ethyl or propyl) or an C1-C8 alkyl group containing a cyclic hydrocarbon structure (such as cycloalkyl such as cyclohexyl or cyclopentyl), an aryl group (preferably containing 6 to 20 carbon atoms which may optionally be substituted by one or more C1-C4 alkyl groups or halogens or mixtures thereof, such as phenyl), an alkylaryl group (preferably containing 7 to 12 carbon atoms) or an aralkyl group (preferably containing 7 to 12 carbon atoms).
For formula IV, Y is hydrolysable group. Suitable and preferred examples of hydrolysable groups include those groups as mentioned with respect to component (A), formula I. Particularly preferred hydrolysable groups include alkoxy groups (preferably containing 1 to 4 carbon atoms), such as methoxy and ethoxy groups.
Particularly preferred reactive compounds according to formula (IV), in which the reactive functional group L is one that reacts by addition or condensation reactions, include epoxypropyltrimethoxysilane), bis(3-aminopropyltrimethoxysilyl)amine and aminopropyltrimethoxysilane.
Alternatively L may be a reactive functional group that is a free radically polymerizable group that typically contains an ethylenically unsaturated group capable of undergoing a free radical polymerization. Suitable free radically polymerizable groups L include, for example, moieties derived from vinyl ethers, vinyl esters, allyl esters, vinyl ketones, styrene, vinyl amide, acrylamides, maleates, fumarates, acrylates and methacrylates. Of these, the esters and amides of alpha, beta unsaturated acids, such as the acrylates and methacrylates are preferred.
Where L is a free radically polymerizable group the organic divalent linking group Q may contain from 1 to about 20, preferably from 1 to 10 carbon atoms. Q can optionally contain oxygen, nitrogen, or sulfur-containing groups or a combination thereof. Examples of suitable linking groups Q include straight chain, branched chain or cyclic alkylene (preferably containing 2 to 20 carbon atoms), arylene (preferably containing 6 to 20 carbon atoms), aralkylene (preferably containing 7 to 20 carbon atoms), oxyalkylene, carbonyloxyalkylene, oxycarboxyalkylene, carboxyamidoalkylene, urethanylenealkylene, ureylenealkylene and combinations thereof.
Preferred linking groups Q for Formula IV are selected from the group consisting of alkylene (preferably containing 2 to 20, more preferably 2 to 10 carbon atoms), oxyalkylene (preferably containing 2 to 20 carbon atoms and 1 to 10 oxygen atoms) and carbonyloxyalkylene (preferably containing 3 to 20 carbon atoms).
Examples of compounds according to formula (IV), wherein L is a free radically polymerizable group include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane and alkoxysilane functionalised acrylates or methacrylates, such as methacryloyloxypropyl trimethoxysilane.
The presence of such reactive functional groups, preferably reactive unsaturated groups in the corresponding polycondensates is advantageous in that following the coating of the composition onto a substrate a two-fold curing can be carried out, i.e. a thermal or photochemically induced linking of the unsaturated organic radicals through radical polymerization and a thermal completion of the polycondensation (e.g. by elimination of water from groups M-OH still present). In the case an unsaturated compound is used, additionally a catalyst should typically be present for the thermal and/or photochemically induced curing of the coating composition applied onto a suitable substrate. Particularly preferred is the addition of a photopolymerization initiator. Such initiators are commercially available and include e.g. Irgacure(copyright) 184 (1-hydroxycyclohexyl phenyl ketone), Irgacure(copyright)500 (1-hydroxycyclohexyl phenyl ketone, benzophenone), and other photo-initiators of the Irgacure(copyright)-type available from Ciba-Geigy; Darocur(copyright)-type photoinitiators, available from Merck, benzophenone and the like.
Examples of optionally employed thermal initiators are known to those skilled in the art and include, among others, organic peroxides in the form of diacyl peroxides, peroxydicarbonates, alkyl peresters, dialkyl peroxides, perketals, ketone peroxides and alkyl hydroperoxides. Specific examples of such thermal initiators are dibenzoyl peroxide, tert-butyl perbenzoate and azobisisobutyronitrile. These initiators are added to the coating composition in amounts known to one skilled in the art. Typically the initiator will be added in an amount between 0.1 and 2% by weight, based on the compounds according to formula IV.
The compositions may further contain additives that provide the coating with additional properties, such as antimicrobial properties. Examples include [C18H37N (CH3)2(CH2)3Si(OCH3)3]+Clxe2x88x92. However, the addition of ionic hydrolysing the hydrolysable groups present in the components and carrying out additives is preferably kept below about 10% by weight, in order not to adversely affect the water repellency properties of the composition.
According to the present invention, it is preferred that the weight ratio of compounds (A) to compounds (B) in the fluorochemical composition is 1:1 to 1:20 and particularly preferred 1:1 to 1:10. The composition of the present invention comprises a substantial amount of component (B), i.e. an amount greater than a catalytic amount. Typically, component (B) comprises more than 10 weight percent and more preferably more than 25 weight percent based on the total weight of the components used. In a particularly preferred embodiment, component (B) comprises more than 50 weight percent based on the total weight of the components used. Compound (C) can be used between 0 and 50%, preferably between 0 and 35% by weight, based on the total weight of the components used.
While the benefits of reacting components A and B (optionally with C) extend over a wide range of compositions, good initial repellency is achieved for coatings despite relatively low levels of the fluorochemical polyether silane (component A). Therefore a preferred embodiment of this invention employs the relatively expensive fluorosilane at 5-20% wt. %, giving an economic advantage to the compositions of this invention over other fluorinated coatings. Additionally, compositions of 5-20 wt. % component A were quite surprisingly more durable in maintaining repellency after abrasion of a coated surface.
In one embodiment, a composition comprising components (A) and (B) and optionally (C), sufficient solvent, water, and acid or base catalyst may be combined and coated onto a suitable substrate. When such a coating is applied to the substrate shortly after its preparation, components (A) and (B) and optionally (C) will generally not have undergone a condensation reaction or if condensation has occurred the amount thereof will be low. Generally, the amount of condensation that takes place prior to coating will depend on the concentration and nature of components (A) and (B) and optionally (C), the temperature and the time between preparation of the coating composition and the coating of the substrate. Generally, the coating composition will contain components (A) and (B) each in amounts between 0.01% by weight and 5% by weight and the coating is typically applied within about 3 to 8 hours from its preparation. The present invention however does not exclude the possibility of coating a composition in which partial condensates have formed. Typically, compositions comprising partial condensates may form when the aforementioned coating composition is left for some time before coating, for example for more than 1 hour. Nevertheless, the coating composition should be applied to the substrate before the condensation reaction proceeds towards completion.
Preferably, the amount of water will be between 0.1 and 20% by weight of the total composition, more preferably between 1 and 10% by weight. In addition to water, an organic or inorganic acid or base catalyst should preferably be used in the coating composition.
Organic acid catalysts include acetic acid, citric acid, formic acid, triflic acid, perfluorobutyric acid and the like. Examples of inorganic acids include sulphuric acid, hydrochloric acid and the like. Examples of useful base catalysts include sodium hydroxide, potassium hydroxide and triethylamine. The acid or base catalyst will generally be used in amounts between about 0.01 and 10%, more preferably between 0.05 and 5% by weight of the total composition.
The composition of the present invention typically includes one or more organic solvents. The organic solvent or blend of organic solvents used must be capable of dissolving a mixture of compounds (A), (B) and optionally (C) and any partial condensate that may form as a result of partial condensation of (A), (B) and optionally (C). Preferably, the organic solvent or blend of organic solvents used is capable of dissolving at least 0.01% of compounds (A), (B), (C) and/or partial condensates thereof. Furthermore, the solvent or mixture of solvents preferably has a solubility for water of at least 0.1%, preferably 1% by weight and a solubility for the acid or base catalyst of at least 0.01%, preferably 0.1% by weight. If the organic solvent or mixture of organic solvents do not meet these criteria, it may not be possible to obtain a homogeneous mixture of the fluorinated polycondensate, solvent(s), water and catalyst.
Suitable organic solvents, or mixtures of solvents can be selected from aliphatic alcohols (preferably containing 1 to 6 carbon atoms), such as methanol, ethanol, isopropylalcohol; ketones such as acetone or methyl ethyl ketone; esters, such as ethyl acetate, methylformate and ethers, such as diethyl ether. Particularly preferred solvents include ethanol and acetone.
Fluorinated solvents may be used in combination with the organic solvents in order to improve solubility of the starting compounds and/or the partial condensate. Such fluorinated solvents will generally not be suitable for use on their own because they will generally not meet the requirements of solubility for water and acid or base unless they additionally contain hydrophilic groups such as CF3CH2OH.
Examples of fluorinated solvents include fluorinated hydrocarbons, such as perfluorohexane or perfluorooctane, available from 3M; partially fluorinated hydrocarbons, such as pentafluorobutane, available from Solvay, or CF3CFHCFHCF2CF3, available from DuPont; hydrofluoroethers, such as methyl perfluorobutyl ether or ethyl perfluorobutyl ether, available from 3M. Various blends of these materials with organic solvents can be used.
The composition comprising the compounds (A), (B), optionally (C) and/or partial condensates thereof is generally applied to the substrate in amounts sufficient to produce a coating that is water and oil repellent. This coating can be extremely thin, e.g. 1 to 50 molecular layers, though in practice a useful coating may be thicker.
Suitable substrates that can be treated in a particularly effective way with the composition of this invention include substrates having a hard surface that preferably has groups capable of reacting with the compounds (A), (B), optionally (C) and/or partial condensates. Particularly preferred substrates include ceramics, glass, metal, natural and man-made stone, thermoplastic materials (such as poly(meth)acrylate, polycarbonate, polystyrene, styrene copolymers, such as styrene acrylonitrile copolymers, polyesters, polyethylene terephthalate), paints (such as those on acrylic resins), powder coatings (such as polyurethane or hybrid powder coatings), inox, chromated steel and wood. Various articles can be effectively treated with the fluorochemical solution of the present invention to provide a water and oil repellent coating thereon. Examples include ceramic tiles, bathtubs or toilets, glass shower panels, construction glass, various parts of a vehicle (such as the mirror or windscreen), glass, and ceramic or enamel pottery materials.
Treatment of the substrates results in rendering the treated surfaces less retentive of soil and more readily cleanable due to the oil and water repellent nature of the treated surfaces. These desirable properties are maintained despite extended exposure or use and repeated cleanings because of the high degree of durability of the treated surface as can be obtained through the compositions of this invention.
To effect the treatment of a substrate, the composition as disclosed above, is applied to the substrate. The amount of compounds (A), (B), optionally (C) and/or partial condensates to be coated on the substrate will generally be that amount sufficient to produce a coating which is water and oil repellent, such a coating having at 20xc2x0 C. a contact angle with distilled water of at least 80xc2x0, and a contact angle with n-hexadecane of at least 40xc2x0, measured after drying and curing of the coating.
Preferably, the substrate should be clean prior to applying the compositions of the invention so as to obtain optimum characteristics, particularly durability. That is, the surface of the substrate to be coated should be substantially free of organic contamination prior to coating. Cleaning techniques depend on the type of substrate and include, for example, a solvent washing step with an organic solvent, such as acetone or ethanol.
The coating composition is typically a relatively diluted solution, containing between 0.01 and 5 percent by weight of compounds (A), (B), optionally (C) and/or partial condensates, more preferably, between 0.03 and 3 percent by weight, and most preferably, between 0.05 and 2 percent by weight.
In accordance with a preferred embodiment, compositions for application to a substrate are prepared by diluting a concentrate comprising a solution of compounds (A), (B) and optionally (C) in an organic solvent that is substantially free of water. Dilution of the concentrate may be effected by adding thereto further organic solvent. To the mixture is also added water and optionally an acid or base catalyst to obtain the coating composition. Preferably, the concentrate from which the coating composition is prepared contains compounds (A) and (B) in their desired weight ratio to each other. In this respect, it has been found that homogeneous concentrates are preferably prepared with compounds (A) that have an alkoxy group of 2 to 4 carbon atoms as the hydrolysable groups on the silyl group. It was found that such compound more easily allow for the preparation of concentrates in which the weight ratio of compounds (B) to compounds (A) is for example between 3:1 to 12:1, preferably 6:1 to 9:1. High weight ratios may be desired in cases where a high UV stability is desired, i.e. where it is desired that the repellency properties are maintained well when the coating is exposed to UV and humidity. On the other hand, lower weight ratios, for example 1:1 to 6:1 may be desired in case transparency of the coating is critical, such as for example when coating on glass.
A wide variety of coating methods can be used to apply a composition of the present invention, such as brushing, spraying, dipping, rolling, spreading, and the like. A preferred coating method for application of the coating composition of the present invention includes spray application. An airless spray application will typically be preferred in cases where transparency of the coating is important. A substrate to be coated can typically be contacted with the treating composition at room temperature (typically, about 15xc2x0 C. to about 30xc2x0 C.). Alternatively, the mixture can be applied to substrates that are preheated at a temperature of for example between 30xc2x0 C. and 150xc2x0 C. This is of particular interest for industrial production, where e.g. ceramic tiles can be treated immediately after the baking oven at the end of the production line. Following application, the treated substrate can be dried and cured at ambient or elevated temperature, e.g. at 40xc2x0 to 300xc2x0 C. and for a time sufficient to dry and cure. The coating compositions of the present invention generally do not require subjecting the compositions to an elevated temperature. Thus, repellent and durable coatings in connection with this invention can be readily obtained upon coating and drying at ambient temperature. Alternatively, in addition with a thermal treatment, the coating composition may be cured by irradiation (e.g. by means of UV-irradiators, a laser, etc.) in a manner known per se, depending on the type and presence, respectively of an initiator. The process may also require a polishing step to remove excess material.
The following examples further illustrate the invention without the intention however to limit the invention thereto. All parts are by weight unless indicated otherwise.
1. Synthesis of Fluorinated Polyether Disilanes
A. Fluoropolyetherdisilane FES-1:
FES-1 was prepared by reacting perfluoropolyetherdiester CH3OC(O)CF2O(CF2O)9-11(CF2CF2O)911 CF2C(O)OCH3 (with average molecular weight of about 2000), commercially available from Ausimont, Italy, under the trade designation Fomblin(trademark) Z-DEAL, with 3-aminopropyltrimethoxysilane, available from Aldrich Co., Milwaukee, Wis., as taught in U.S. Pat. No. 3,810,874 (Mitsch et al.), table 1, line 6. The exothermic reaction proceeded readily at room temperature, simply by mixing the starting materials. The progress of the reaction was monitored by infrared analysis.
B. Fluoropolyetherdisilane FES-2:
FES-2 was prepared by reacting perfluoropolyetherdiester Fomblin(trademark) Z-DEAL, with 3-aminopropyltriethoxysilane, available from Aldrich Co. Milwaukee, Wis., essentially as taught in U.S. Pat. No. 3,810,874 (Mitsch et al.), table 1, line 6. The exothermic reaction proceeded readily at room temperature, simply by mixing the starting materials. The progress of the reaction was monitored by infrared analysis.
C. Preparation of FES-3:
The hydrocarbon, organic starting material CH3OCOC2H4O(CH2)6OC2H4COOCH3 was prepared by base-catalyzed Michael addition of 1,6-hexanediol (Aldrich, Milwaukee, Wis.) to two equivalents of acrylonitrile, followed by acid-catalyzed methanolysis. The methyl ester was directly fluorinated with F2 to produce the perfluorinated derivative CF3OCOC2F4O(CF2)6OC2F4COOCF3. The method followed was essentially that found in U.S. Pat. No. 5,578,278 (Fall et. al.). The crude perfluorinated ester was treated with 150 mL of 14% BF3 in methanol and agitated vigorously for 24 hrs. The mixture was washed with water and dried over MgSO4 and distilled (100-110xc2x0 C.@0.3 torr) to yield CH3OCOC2F4O(CF2)6OC2F4COOCH3. CH3OCOC2F4O(CF2)6OC2F4COOCH3 was further reacted with two equivalents of 3-aminopropyltriethoxysilane (available from Gelest, Inc, Tulleytown, Pa.) in ethanol. The reaction was followed by infrared analysis, and when complete, the solvent was stripped on a rotary evaporator to yield a colorless to light tan fluid (C2H5O)3Si(CH2)3NHC(O)C2F4O(CF2)6OC2F4C(O)NH(CH2)3Si(OC2H5)3 (FES-3).
D. Preparation of FES-4:
The procedure as described for FES-3 was followed, starting with 2,2-dimethyl-1,3-propandiol and acrylonitrile to yield CH3OCOC2H4OCH2C(CH3)2CH2OC2H4COOCH3. Upon direct fluorination, CF3OCOC2F4OCF2C(CF3)2CF2OC2F4COOCF3 was produced. This was reacted with 3-aminopropyltriethoxysilane to yield (C2H5O)3Si(CH2)3NHCOC2F4OCF2C(CF3)2CF2OC2F4CONH(CH2)3Si(OC2H5)3 (FES-4).
E. Preparation of FES-5:
Using methods similar to those described in U.S. Pat. No. 5,658,962 (Moore et. al.) tetraethyleneglycol diacetate was fluorinated and methanolyzed to yield CH3OCO(CF2OCF2)3COOCH3 (b.p. 70xc2x0 C./0.5 torr), plus a minor amount of CF3OCF2(CF2OCF2)2CO2CH3 produced by apparent decarboxylation during fluorination. The fluorinated ester was reacted with two equivalents 3-aminopropyltriethoxysilane in ethanol. The reaction was followed by infrared analysis, and when complete, the solvent was stripped on a rotary evaporator to yield a colorless to light tan fluid (C2H5O)3Si(CH2)3NHCO(CF2OCF2)3CONH(CH2)3Si(OC2H5)3 (FES-5).
F. Synthesis of FES-6 to FES-10:
Using methods and techniques as described for the synthesis of FES-3, other perfluoropolyetherdisilanes (FES-6 to FES-10) were prepared starting from the hydrocarbon starting materials (number indicative of number average Mw), as given in table 1. The perfluorinated esters were distilled at a temperature and pressure as given in table 1. Two fractions were obtained from the reaction starting from Polytetramethylene oxide 650. Accordingly, two perfluoropolyetherdisilanes FES-9 and FES-10 were prepared from the same hydrocarbon starting material. F-NMR was used to characterize the % functionality of the perfluorinated ester.
2. Methods of Application
Spray Application
The substrates were cleaned and degreased with acetone and kept at room temperature before coating. Alternatively, the substrates were preheated before coating.
(i) Spray Application With Air
Fluorochemical treating compositions given in the respective examples were applied onto the substrates, by spray application using a spray gun operating with air (Venturi principle).
(ii) Airless Spray Application
The fluorochemical treating composition was supplied to the substrate, by means of a spray gun without the use of air. The composition was sprayed onto the substrates by means of a 730073 SS nozzle (available from Spraying Systems).
Coated samples were dried at room temperature or forced-air oven dried at a temperature between 80xc2x0 C. and 150xc2x0 C. for 30 minutes. Afterwards, excess product was polished off using a dry or wet paper wipe.
Dip Application
(i) One Bath Dip Application: a substrate, cleaned by acetone, was dipped in a bath comprising component (B)(eg. TEOS), fluorochemical polyether disilane, acid, water and ethanol. After removal from the bath, the treated substrate was dried at room temperature for about 20 min. After drying, the excess product was removed using a dry cloth.
(ii) Two Bath Dip Application: a substrate, cleaned by acetone, was dipped in a bath containing component (B) (eg. TEOS). The substrate was air dried at room temperature and then dipped in a second bath comprising fluorochemical polyether disilane, acid, water and ethanol. After removal from the bath, the substrate was dried at room temperature for about 20 min. After drying, the excess product was removed using a dry cloth.
Flow Coating
The fluorochemical treating composition was applied using a syringe or a pipette, across the top of the vertical held substrate. This method is also referred to as curtain coating.
After allowing excess solution to drain away, the substrates were placed in an oven at 90xc2x0 C. for 15 minutes.
3. Testing
Static Contact Angles
The treated substrates were tested for their contact angles versus water and n-hexadecane using an Olympus TGHM goniometer. The values are the mean values of 4 measurements and are reported in degrees. The minimum measurable value for a contact angle was 20. A value less than 20 meant that the liquid spread on the surface.
Advancing and Receding Contact Angles
Advancing and receding contact angles were measured on nylon film, treated with the fluorochemical disilane composition at about 3% solids, by dip application (one bath). A 85 mmxc3x9713 mm rectangular strip of nylon film was cleaned by dipping into methyl alcohol and wiping with a KIMWIPE(trademark) wiper (commercially available from Kimberly-Clark Corp., Neenah, Wis.), taking care not to touch the strip""s surface. The strip was allowed to dry for 15 minutes. Then, using a small binder clip to hold one end of the strip, the strip was immersed in the treating solution, and the strip was then withdrawn slowly and smoothly from the solution. The coated film strip was tilted to allow any solution run-off to accumulate at the corner of the strip, and a KIMWIPE(trademark) wiper was touched to the corner to pull away the solution build-up. The coated film strip was allowed to air dry in a protected location for a minimum of 30 minutes and then was cured for 10 minutes at 121xc2x0 C.
Advancing and receding contact angles were measured using a CAHN Dynamic Contact Angle Analyzer, Model DCA 322 (a Wilhelmy balance apparatus equipped with a computer for control and data processing, commercially available from ATI, Madison, Wis., calibrated using a 500 mg weight). An alligator clip was fastened to a piece of coated film strip about 30 mm long, and the clip and film piece were hung from the stirrup of the balance. A 30 mL glass beaker containing approximately 25 mL of water or n-hexadecane was placed under the balance stirrup, and the beaker was positioned so that the coated film strip was centered over the beaker and its contents, but not touching the walls of the beaker. Using the lever on the left side of the apparatus, the platform supporting the beaker was carefully raised until the surface of water or n-hexadecane was 2-3 mm from the lower edge of the film strip. The door to the apparatus was closed, the xe2x80x9cConfigurexe2x80x9d option was chosen from the xe2x80x9cInitializexe2x80x9d menu of the computer, the xe2x80x9cAutomaticxe2x80x9d option was chosen from the xe2x80x9cExperimentxe2x80x9d menu, and the computer program then calculated the time for a scan. The apparatus then raised and lowered the liquid so that the scan was taken (the advancing angle was measured as the liquid moved up and over the surface, while the receding angle was determined as the liquid moved down and away from the surface of the plastic film). The xe2x80x9cLeast Squaresxe2x80x9d option was selected from the xe2x80x9cAnalysisxe2x80x9d menu, and the average receding contact angle was calculated from the scan of the film sample. Three separate films were prepared for each material to be tested as previously described. The 95% confidence interval for the average of the 3 scans was typically about 1.2xc2x0. This procedure was repeated for water and n-hexadecane.
Aging Test
Treated glass samples were aged in a QUV-apparatus, following the ASTM-standard G.53-84. UV fluorescent lamps of type UVB-313 were used for the light source.
The test cycle was UV-illumination without humidification for 8 hours at a temperature of about 60xc2x0 C., followed by humidification without UV-illumination, for 4 hours at a temperature of about 50xc2x0 C.
Tilt Angle
A treated substrate was placed in a Tilt Angle Instrument. 3 drops or about 100 xcexcliter water were placed on the surface of the treated substrate. The substrate was tilted and the angle at which the drops start rolling off the surface was reported. The values, reported in degrees (xc2x0) are the mean values of 3 measurements. The maximum recordable value was 70xc2x0.